Conventionally, rotating electric machines, such as an electric motor and a generator, which include a stator and a rotor, are known. The stator of a rotating electric machine is generally manufactured as follows. While a plurality of substantially annular steel plates are first stacked in layers so as to produce a stator core, a plurality of coil elements which are formed substantially in the shape of a letter U by bounding a plurality of electrical conductors are produced. Then, the produced coil elements are aligned annularly while being overlaid in a circumferential direction, and in this state, the tip end portions of the electrical conductors are inserted through slots aligned annularly in the stator core. Then, the tip end portions of the electrical conductors which are protruded from the slots are twisted in a circumferential direction, and are thereafter joined together. Then, parts of the surfaces of the electrical conductors exposed from the slots are coated with a resin, and thus insulation processing is performed. In this way, the stator of a rotating electric machine is manufactured.
Incidentally, the insulation processing described above is performed by heating the stator core by induction heating and then coating the electrical conductors heated to a high temperature with a powder resin. However, the steel plates are affected by magnetic field lines produced at the time of heating, thus magnetic levitation occurs, the heat is not transmitted to lower layers below the levitated layer and only the levitated steel plates are overheated, with the disadvantageous result that, for example, the heat-resistant temperature of insulating paper is exceeded or that the steel plates are thermally deformed. Hence, as a method of mitigating the curving and the magnetic levitation of the steel plates, a method of arranging on the steel plates a holding plate formed with an annular nonmagnetic member (see, for example, patent document 1) and a method of installing a weight on the steel plates (see, for example, patent document 2) are proposed.
On the other hand, in the stator core, a plurality of fastening holes for fixing the steel plates stacked in layers are provided. Hence, when a resin is applied, a foreign substance such as a powder resin or varnish may be adhered to the surrounding of these fastening holes such that a fastening surface is not brought into close contact with a washer and thus a problem may occur in a fastening operation. Hence, conventionally, an operator covers the vicinity of the fastening holes with masking tape, and in this state, the coating of the resin is performed.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2012-240254
Patent Document 2: Japanese Unexamined Patent Application, Publication No. S60-74417